How is a brain injury classified? as an injury of the peripheral nervous system
as an injury of the central nervous system
as an injury of the autonomic nervous system
as an injury of the somatic nervous system

As an injury of the central nervous system.

Explanation:

Peripheral nervous system is the nervous system outside the brain and spinal cord. The central nervous system consists of the brain and spinal cord. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, digestion, respiratory rate, and more. The somatic nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles. Therefore, central nervous system is your answer!

Hope this helps :3